Provisioning Logic

Modify the default provisioning of the APS PHP framework by your own definition of the synchronous and asynchronous operations.

Operations

The updates concern the vpses service that together with the APS controller and APS PHP framework must function as follows:

1. The APS controller, when sending the POST request to the vpses service for creating a VPS in the sync mode, specifies if the VPS will be a container (sharing the OS kernel with other containers) or a VM (virtual machine with its own OS kernel).

2. The APS PHP framework will transfer the sync POST request to the provision operation defined in the vpses service.

3. If the required VPS must be a container, the provision method confirms the creation of the new VPS immediately by sending the 200 OK response to the APS controller. This will complete the operation in the sync mode.

4. If the required VPS must be a VM with its own OS kernel, the provision method returns the 202 Accepted code. It also specifies the time-out and the description for the task that the APS controller must schedule.

5. The APS controller is sending the POST request in the async mode until it receives a return code different from 202 Accepted.

6. The APS PHP framework transfers the async POST request to the provisionAsync operation defined in the vpses service.

7. To simulate a long-running operation, the vpses service will require the APS controller to repeat a POST request in the async mode 5 times with the time-out 5 seconds.

Continue Your Demo Project

This section continues the demo project started in the previous step.

Modify the vpses service and respective APS type in the vpses.php file as follows.

1. To influence the provisioning process, add the VM property in the Hardware class:

   /**
    * @type("boolean")
    * @title("VM with separate OS kernel or Container using shared OS kernel")
    * @description("VM requires more time for provisioning - async POST")
    */
   public $VM;
   

   This property will allow subscribers to select the VPS type, either VM (VM=true) or container (VM=false). Depending on this, the application provisions the required VPS using the async or sync method respectively.

2. To count the number of calls on the async provisioning, add the retry property to the main vps class.

   /**
    * @type("integer")
    * @title("Counter for async operation")
    * @description("Counts the number of retries for async operation")
    */
   public $retry;
   

3. Define the sync provision operation in the main vps class:

   // Provision method is called when a sync provisioning is requested
   public function provision() {
            // VM requires more time, thus the *async* operation is required
        if ($this->hardware->VM) {
            $this->state = "Creating"; // Intermediate VPS state
            throw new \Rest\Accepted($this, "Creating VPS", 5); // Return "202 Accepted"
        } else {
            // Simulate the end of async provisioning to show correct status in UI
            $this->retry = 5;
        }
   }
   

   When a container is requested ($this->hardware->VM==false), the method does nothing, and the APS PHP framework returns 200 OK, thus completing the requested operation successfully in the sync mode. When a long running provisioning is requested (creating a VM), the provision() method will throw a predefined exception processed properly by the APS PHP framework. This will cause sending an HTTP 202 Accepted response. After getting such a response, the APS controller must schedule a task for sending a request for the async provisioning. The exception contains the task description (“Creating VPS” in the example above) and time-out (5 s) for the task launch.

4. Add the async provisioning operation in the main vps class:

   public function provisionAsync() {
        $this->retry +=1; // Increment the retry counter
        if ($this->retry >= 5) {
            $this->state = "Stopped"; // Finish the Async operation - return "200 OK"
        }
        else {
            throw new \Rest\Accepted($this, "Creating VPS", 5); // Return "202 Accepted"
        }
   }
   

   The provisionAsync() method returns 202 Accepted with proper task description and time-out until the application completes the requested provisioning. Once, the request is completed (simulated by reaching the 5th retry), it returns 200 OK.

Conclusion

This completes modification of the vpses.php file, which is a part of the provisioning logic. You can compare the added code with the contents in the respective file inside the sample package.

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